Memory circuits to which data may be written and stored and from which the stored data may read are widely used in a number of applications. One such application is in the field of electronic voting machines or other types of preference expression devices. Electronic voting machines may comprise at least a voting station where a voter casts votes for various candidates, referenda, etc. These votes may be recorded by storing data representative of the voter's selections in a removable tally module associated with the voting station or remote therefrom. This tally module comprises a memory device. It is very important that the data stored in this memory device be secure to preserve the integrity of the election process. In a multi-district election, e.g., the tally module from each district may be removed after the polls are closed and delivered to election authorities so that the data stored in the tally modules may be read.
Various safeguards may be implemented to protect against election fraud during the voting process. However, it is also very important to safeguard the data after the polls close so that between the time the polls close and the time the memory device is presented to the central election authorities, no unauthorized alteration of the stored data may occur.